There is a standard procedure how most email hosting services work.
You send email via SMTP through port 587. For encrypted connection you use STARTTLS. Sometimes you can use port 25, but that's non-standard for submitting mails. Also, you can use port 465 for encrypted connection without STARTTLS, but that's non-standard.
For receiving email you use POP or IMAP. People prefer one or the other. POP is more simple, IMAP is more advanced.
For POP you use port 110, STARTTLS for encryption. Alternatively, you use port 995 for encrypted connection without STARTTLS, which is also standard and a matter of choice.
For IMAP you use port 143, STARTTLS for encryption. Or 993 for encryption without STARTTLS, which is also standard.
